Threaded device with metal to metal seal and method

ABSTRACT

A device including a metal to metal seal. The device includes a first section having a first threaded portion. A second section having a second threaded portion threadably engageable with the first threaded portion. A metal bump seal protruding radially from the first section and spaced from the first threaded portion, wherein a radially directed seal is formed with the second section. Also included is a method for sealing a device.

BACKGROUND

Metal to metal seals may be utilized in lieu of elastomeric seal ringsto seal in bores in downhole well tools in hostile environments, such ashigh-pressure and/or high-temperature environments, when the use ofelastomeric sealing materials face limits with respect to reliabilityand durability. Seal failures can have undesirable consequences, requirecostly repairs, and cause lost production. Metal to metal seals havebeen shown to have significant reliability, durability and resistance inthe most extreme conditions. Conventional metal to metal sealsincorporate load shoulders which must make contact in order to achievethe appropriate seal. That is, such static metal to metal seals consistof a face seal that must be compressed into a seat for the seal to work.Should the seal be moved even slightly, then the integrity of the sealwould be compromised. As oil and gas wells have been drilled intoformations experiencing increased pressure and in deeper and deeperocean waters, a need exists for reliable metal to metal sealing betweensections of wellbore tools.

BRIEF DESCRIPTION

A device including a metal to metal seal, the device includes a firstsection having a first threaded portion; a second section having asecond threaded portion threadably engageable with the first threadedportion; and a metal bump seal protruding radially from the firstsection and spaced from the first threaded portion, wherein a radiallydirected seal is formed with the second section.

A method of sealing a device including a first tubular section and asecond tubular section, the method includes threadably connecting thefirst tubular section to the second tubular section with a threadedconnection; engaging a first metal bump seal adjacent a first end of thethreaded connection between the first and second tubular sections toform a radially directed metal to metal seal at a first contact stress;and applying pressure to create a second contact stress higher than thefirst contact stress with the metal bump seal.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a cross-sectional view of an exemplary embodiment of athreaded device incorporating a metal to metal seal usable in a wellboretool;

FIG. 2 is a cross-sectional view of another exemplary embodiment of athreaded device incorporating a metal to metal seal; and,

FIG. 3 is a cross-sectional view of yet another exemplary embodiment ofa threaded device incorporating a metal to metal seal.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

With reference to FIG. 1, in one exemplary embodiment, a device 30including a metal to metal seal incorporates metal bump seals 32, 34 atboth ends of a threaded connection 36, that is, the lead in area 38before thread 36 and the lead out area 40 after the thread 36. Inanother exemplary embodiment shown in FIG. 2, a device 50 including ametal to metal seal incorporates the metal bump seal 34 at a first endof a threaded connection 36, such as the lead out area 40 of thethreaded connection 36, and in yet another exemplary embodiment shown inFIG. 3, a device 60 includes a metal to metal seal that incorporates themetal bump seal 32 at a second end of a threaded connection 36, such asthe lead in area 38 of the threaded connection 36.

As is understood in the art of threaded connections, the screw thread isa helical structure used to convert between rotational and linearmovement. A screw thread is a ridge wrapped around a cylinder or cone inthe form of a helix. A threaded connection includes both a sectionhaving an external thread, also known as a male portion or vernacularlya pin thread, and a section having an internal thread, also known as afemale portion or vernacularly a box thread. In one exemplaryembodiment, the section having the external thread may be one of aliner, liner hanger, casing, production string, work string, drillstring, or other tubular connections that may benefit from a metal tometal seal, and the section having an internal thread may be another ofa liner, liner hanger, casing, production string, work string, drillstring, or other tubular connection, such that the sections arethreadably secured together by the threads and sealed together by themetal to metal seal. When the device is used in a downhole environment,the device may be sealed such that an inner annulus is sealed from anouter annulus._([mmh1]) As will be further described below, the use ofthe device in a downhole environment takes advantage of the pressurewithin the downhole environment to assist in the sealing process of themetal to metal seal. However, the device may also be employable in areasoutside of a downhole environment. Thus, a first tubular section thatemploys internal or external threads is threaded and sealed to a secondtubular section that employs the other of internal or external threadsusing the metal to metal seal of the present invention. For the purposesof this description, the first tubular section will be described as abox 42 and incorporates the internal threads 44 on its inner diameterand the second tubular section will be described as a pin 46 andincorporates the external threads 48 on its outer diameter. Also asshown in FIGS. 1-3, in an exemplary embodiment, the box 42 and the pin46 employ tapered conical faces that carry the threads 44, 48 on theirrespective inner and outer faces. However, in an alternative exemplaryembodiment, the box 42 and pin 46 may include cylindrical inner andouter thread carrying faces.

The metal bump seals 32, 34 are shown as integrally formed bumps thatextend from the pin 46. As shown in FIGS. 1 and 3, a first bump 32 isprovided on the lead in area 38 before the thread 36, and as shown inFIGS. 1 and 2, a second bump 34 is provided on the lead out area 40after the thread 36. The first bump 32 is spaced a first distance D1from the first end of the threaded connection 36 and the second bump 34is spaced a second distance D2 from the second end of the threadedconnection 36.

While the threads 36 are helically arranged about the outer diameter ofthe pin 46 and box 42, the first and second bumps 32, 34 may radiallysurround the pin 46 or radially protrude from an interior of the box 42.A cross-section of the bumps 32, 34 may by rounded, such assemi-circular shaped, however other cross-sections are also within thescope of these embodiments, including, but not limited to, flattenedcurved shapes, rectangular shapes, trapezoidal shapes, etc. The shape isselected to provide an interference fit with a mating portion of the pin46 or box 42. Also, while the metal bump seals 32, 34 are shown asextending from the outer diameter of the pin 46, they may also extendfrom the inner diameter of the box 42. In yet another exemplaryembodiment, the first bump 32 may extend from one of the pin 46 and thebox 42 and the second bump 34 may extend from the other of the pin 46and the box 42. While the first and the second bumps 32, 34 aredescribed and shown as manufactured integrally with the pin 46 and/orthe box 42, it is also within the scope of these embodiments to add thefirst and second bumps 32, 34 subsequent to the manufacture of the pin46 and/or the box 42, such as by welding the metal bumps _([mhh2]) 32,34 thereon or therein. In such an exemplary embodiment, the weldedmaterial may or may not be identical to the base material.

As shown in FIG. 1, the inclusion of bumps 32, 34 on both the box 42 andthe pin 46 creates an atmospheric pressure trap between the bumps 32,34, which, when the device 30 is run into a well bore, facilitates theinitial sealing mechanism. That is, the interference fit between thefirst and second bumps 32, 34 and their respective mating portions onthe box 42 or pin 46 generates a first contact stress. Then, when thedevice 30 is run into a well bore, pressure is applied from the downholeenvironment and the differential pressure creates a second contactstress greater than the first contact stress. Thus, with the first andsecond bumps 32, 34 at opposing ends of the threaded connection 36, theatmospheric pressure trap is created between the first and second bumps32, 34.

The bumps 32, 34 can be manufactured on either the box 42 or the pin 46,depending on which direction the pressure is desired to be held, thatis, external pressure as shown in FIG. 2, internal pressure as shown inFIG. 3, or both as shown in FIG. 1. The bumps 32, 34 can be used singlyon just the pin 46, or singly on just the box 42, or dually on both thebox 42 and the pin 46. However, should the device, such as device 50 ordevice 60, be manufactured with only one bump seal 32, 34, either on thebox 42 or the pin 46, the device 50 or 60 will still function, but willnot have the advantage provided by the atmospheric pressure trap as withdevice 30.

The bumps 32, 34 are manufactured with an interference fit relative tothe mating part or surface. The mating surface, that is the part uponwhich the bumps 32, 34 engage in operation, may include surfacepreparation, such as a coating, to prevent galling during assembly forlong term corrosion prevention, which inevitably assists in the sealingbetween the bumps_([mhh3]) 32, 34 and their respective mating surfacesby prolonging the life of the surfaces. In some exemplary embodiments,surface preparations may include surface treatments for the bumps 32, 34such as surface hardening, for example, ion nitriding or carburization.Surface preparations may also include polished finishes on the matingsurfaces opposite the bumps 32, 34. _([mhh4] [mhh5]) Upon application ofpressure, such as from a downhole environment, the differential pressurecreates a higher contact stress, that is, provides boost, and the bump32 or 34 seals even tighter thereby allowing application of highpressures.

Another advantage of using these embodiments of the metal to metal seal32, 34 is that it is able to accommodate differences in makeup loss ofthe connection itself. That is, while other styles of metal to metalsealing threads incorporate load shoulders which must make contact inorder to achieve the appropriate seal, the exemplary embodiments of theseal of the present invention can land anywhere on its mating surfaceand still be able to create a seal.

Thus, a metal to metal seal capable of sealing a threaded connection 36between a box 42 and pin 46 has been described. The metal to metal sealincorporates a first and/or second bump 32, 34 to form a radiallydirected seal between the box 42 and pin 46. The metal to metal seal isable to fit in small cross sectional areas, utilizes initial contactstress to initiate the seal at low pressures and utilizes appliedpressure to generate boost pressure for high pressure sealing. Also, themetal to metal seal advantageously accommodates variations in threadmakeup lengths and does not depend on landing on a torque shoulder tocreate the seal. Thus, a method of sealing a threaded connection 36using the metal to metal seal is made possible. Additionally, by runninga device incorporating the threaded connection 36 in a downholeenvironment, the pressure within the environment facilitates the initialsealing mechanism to create a higher contact stress.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited. Moreover, theuse of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another. Furthermore, the use of the termsa, an, etc. do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced item.

1. A device including a metal to metal seal, the device comprising: afirst section having a first threaded portion; a second section having asecond threaded portion threadably engageable with the first threadedportion; and a metal bump seal protruding radially from the firstsection and spaced from the first threaded portion, wherein a radiallydirected seal is formed with the second section.
 2. The device of claim1, wherein the first and second threaded portions include one ofstraight or tapered threads.
 3. The device of claim 1, wherein the firstand second sections are tubular.
 4. The device of claim 3, wherein thefirst section is one of a liner hanger, liner, casing, productionstring, work string, and drill string and the second section is anotherof a liner hanger, liner, casing, production string, work string, anddrill string.
 5. The device of claim 1, wherein the metal bump seal isintegrally formed with the first section.
 6. The device of claim 1,wherein the first section and the second section are made from metal. 7.The device of claim 1, wherein the metal bump seal is a first metal bumpseal adjacent a lead in area of the first threaded portion, and furthercomprising a second metal bump seal provided on one of the first sectionand the second section and adjacent a lead out area of the firstthreaded portion or second threaded portion.
 8. The device of claim 7,wherein an atmospheric pressure trap is created between the first andsecond metal bump seals.
 9. The device of claim 1, wherein the metalbump seal includes a cross-section forming an interference fit with amating surface of the second section.
 10. The device of claim 1, whereinthe second section includes a mating surface engaged with the metal bumpseal and provided with a surface preparation including a coating. 11.The device of claim 1, wherein the metal bump seal is adjacent a lead inarea of the first threaded portion.
 12. The device of claim 1, whereinthe metal bump seal is adjacent a lead out area of the first threadedportion.
 13. The device of claim 1, wherein the metal bump sealgenerates a first contact stress between the first and second sections.14. The device of claim 13, wherein, upon application of externalpressure, a second contact stress higher than the first contact stressis generated between the first and second sections.
 15. The device ofclaim 14, wherein the device is run in a downhole environment to applythe external pressure.
 16. The device of claim 15, wherein the metalbump seal is a first metal bump seal adjacent a lead in area of thefirst threaded portion, and further comprising a second metal bump sealprovided on one of the first section and the second section and adjacenta lead out area of the first threaded portion or second threadedportion.
 17. The device of claim 16, wherein, upon application of theexternal pressure, an atmospheric pressure trap is created between thefirst and second metal bump seals.
 18. A method of sealing a deviceincluding a first tubular section and a second tubular section, themethod comprising: threadably connecting the first tubular section tothe second tubular section with a threaded connection; engaging a firstmetal bump seal adjacent a first end of the threaded connection betweenthe first and second tubular sections to form a radially directed metalto metal seal at a first contact stress; and applying pressure to createa second contact stress higher than the first contact stress with themetal bump seal.
 19. The method of claim 18, wherein applying pressureincludes running the device into a wellbore.
 20. The method of claim 19,further comprising engaging a second metal bump seal adjacent a secondend of the threaded connection and creating an atmospheric pressure trapbetween the first and second metal bump seals.